Various kinds of adsorbents made of polymers inorganic substances (such as, for example, glass and diatomaceout earth) or metals in the form of powder, fiber, fabric, sintered mass, etc. have been suggested to date. Though these known adsorbents show excellent adsorbing ability in their specifiic field of application, they are not always satisfactory in terms of other properties required from the standpoint of commercial uses to which they are put. If a given adsorbent is comminuted for the purpose of improving its adsorbing effect, for example, the comminuted adsorbent causes clogging of a filter which is to be used in the subsequent treatment of filtration for the separation of adsorbent. Consequently, the adsorbent brings about of degradation of the treating speed and it tends to drift away in the form of aerosol or dust, rendering its handling difficult.
Ion-exchange resins are representative of polymer adsorbents and are widely utilized for industrial purposes. The salient disadvantage of ion-exchange resins is that their adsorbing activities are influenced by the electric charage and the size of substances to be adsorbed. Thus, they are deficient of universality over a complete range of conditions of use.
It is the use of porous polymer that one is quite readily conceived of with respect to polymer adsorbents or filters. There have been suggested various method for the manufacture of porous polymer substances such as by the incorporation of foaming agents, for example. In the case of a technique which relies for the formation of pores upon the use of such foaming agents, the control of pore sizes proves to be extremely difficult. Products made by this technique may satisfactorily be utilized as heat insulators, sound absorbers and other similar shock absorbers but have not yet been qualified for use as adsorbents or filters.
In recent years, membrane filters and other similar polymer membranes containing fine pores which are manufactured by effective use of special techniques have come to be utilized as filters for the separation of microscopic substances. These screen type filters have an advantage that the diameter of pores to be contained therein can be selected as desired and the filters are therefore capable of filtering substances of widely varying particle diameters. On the other hand a disadvantage is that substances having particle diameters smaller than the diameter of pores contained therein are passed completely. For example, a screen type filter is capable of removing a pigment, yeast, etc. dispersed in water but is ineffective for the removal of dye, chlorine and other molecules dissolved in aqueous solutions. Conventional adsorbents such as activated carbon and bone black are advantageously used for the adsorption of molecules dissolved in solutions but are least suitable for the adsorption of substances dispersed in liquids. That is to say, conventional filters have an exclusive function of effecting desired separation by filtration and conventional adsorbents have a sole function of providing desired separation by adsorption.
It is a primary object of this invention to provide novel polymer adsorbents excelling in adsorbing activity and enjoying high treating efficiency. It is another object of this invention to provide adsorbents possessed of adsorbing properties which make them suitable for a wide range of purpose of adsorption, i.e. adsorbents capable of adsorbing two or more different substances at the same time. It is still another object of this invention to provide adsorptive filters combining an adsorbing property and a filtering property.